Aldol reaction under solvent-free conditions: highly stereoselective synthesis of 1,3-amino alcohols

[formula: see text] A method for the highly stereoselective synthesis of 1,3-amino alcohols based on the indium trichloride-catalyzed Mukaiyama aldol reaction of keto ester (R,S)-1 under solvent-free conditions has been developed. The high selectivity observed can be explained on the basis of the shielding of one face by a remote substituent.     

Structural studies on cycloadducts of furan, 2-methoxyfuran, and 5-trimethylsilylcyclopentadiene with maleic anhydride and N-methylmaleimide

The early stages of the retro-Diels-Alder reaction are clearly apparent in the structures of the cycloadducts formed between furan or 5-trimethylsilylcyclopentadiene with maleic anhydride and N-methylmaleimide. The degree of lengthening of the C-C bonds that break in this reaction is clearly related to the known reactivity of these cycloadducts toward this reaction. In the structures of the cycloadducts 21 and 22 derived from 2-methoxyfuran, the early stages of an alternative fragmentation reaction are apparent, consistent with the reactivity of these compounds in solution.     

Reagent Precoated Targets for Rapid In-Tissue Derivatization of the Anti-Tuberculosis Drug Isoniazid Followed by MALDI Imaging Mass Spectrometry

Isoniazid (INH) is an important component of front-line anti-tuberculosis therapy with good serum pharmacokinetics but unknown ability to penetrate tuberculous lesions. However, endogenous background interferences hinder our ability to directly analyze INH in tissues. Chemical derivatization has been successfully used to measure isoniazid directly from tissue samples using matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS). MALDI targets were pretreated with trans-cinnamaldehyde (CA) prior to mounting tissue slices. Isoniazid present in the tissues was efficiently derivatized and the INH-CA product measured by MS/MS. Precoating of MALDI targets allows the tissues to be directly thaw-mounted and derivatized, thus simplifying the preparation. A time-course series of tissues from tuberculosis infected/INH dosed animals were assayed and the MALDI MS/MS response correlates well with the amount of INH determined to be in the tissues by high-performance liquid chromatography (HPLC)-MS/MS.     

Tetracarbonyliron adducts of Cp2Cr2(CO)4(μ-η2-P2). Syntheses and crystal structures of Cp2Cr2(CO)4P2[Fe(CO)4] m (m=1 and 2)

Cp₂Cr₂(CO)₄( - ² - P₂), 1, reacts with one molar equivalent of Fe₂(CO)₉ in THF to yield the mono- and di-iron complexes, Cp₂Cr₂(CO)₄P₂[Fe(CO)₄], 2, (16.5% yield) and Cp₂Cr₂(CO)₄P₂[Fe(CO)₄]₂, 3, (16.9% yield), as dark magenta brown and dark greenish brown crystals, respectively. Both complexes were characterized by single-crystal X-ray diffraction analysis. Crystal data –2: space group =P2₁/c,a=17.024(1) Å,b=8.180(1) Å,c=30.891(2) Å, =100.953(5)°,V=4223.4(7)ų,Z=8, 3743 observed reflections,R _F=0.033; 3: space group P1,a=10.209(2) Å,b=10.212(2) Å,c=15.989(3) Å, =106.93(1)°, =91.87(1)°, =119.50(1)°,V=1356.5(4) ų,Z=2, 3489 observed reflections,R _F=0.029.     

Self‐assembly of di‐ and triblock PEG‐pentavaline amphiphiles

Nanoparticles formed from amphiphilic block copolymers can be used as drug delivery vehicles for hydrophilic therapeutics. Poly(ethylene glycol) (PEG)‐peptide copolymers were investigated for their self‐assembling properties and as consequent potential delivery systems. Mono‐ and dihydroxy PEGs were functionalized with a pentavaline sequence bearing Fmoc end groups. The molecular weight of the PEG component was varied to evaluate copolymer size and block number. These di‐ and tri‐block copolymers readily self‐assemble in aqueous solution with critical aggregation concentrations (CACs) of 0.46–16.29 μM. At concentrations above the CAC, copolymer solutions form spherical assemblies. Dynamic light scattering studies indicate these aggregates have a broad size distribution, with average diameters between 33 and 127 nm. The copolymers are comprised β‐conformations that are stable up to 80 °C, as observed by circular dichroism. This peptide secondary structure is retained in solutions up to 50% MeOH as well. The triblock copolymers proved to be the most stable, with copolymers synthesized from 10 kDa PEG having the most stable particles. Loading of carboxyfluorescein at 2–5 mol % shows that these copolymers have the potential to encapsulate hydrophilic drugs for delivery applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Copolymerization of methacrylonitrile with p-methylstyrene

Methacrylonitrile was copolymerized with p-methylstyrene in methyl ethyl ketone at 80°C initiated by azobisisobutyronitrile. Monomer reactivity ratios of methacrylonitrile and p-methylstyrene were found to be 0.205 and 0.377, respectively, using the Kelen-Tüdos method. Triad fractions and monomer sequence lengths of three copolymers were determined from ¹³C-NMR spectra and were found to be in good agreement with those calculated from reactivity ratios. © 1994 John Wiley & Sons, Inc.     

A New Method of Synthesis of Monomeric Aryloxide Complexes of Manganese(II): Structures of Manganese Phenoxides

Monomeric manganese(II) complexes of bulky alkyl/ aryl‐substituted phenoxides, [Mn{C₆H_nR_mO}₂(DME)] [ 1 : R = C₆H₅, n = 3, m = 2 (2,6); 2 : R = Me₃C, n = 3, m = 2 (2,6); 3 : R = Me₃C, n = 2, m = 3 (2,4,6)] were prepared in yields of 37, 44 and 72 %, respectively, from the reaction of manganese powder, Hg(C₆F₅)₂ and the corresponding phenol in the presence of a little mercury in dimethoxyethane (DME). The compounds were characterized spectroscopically and by magnetic measurements. The single crystal structures of 1 and 3 and also of the mixed phenoxide complex [Mn{(C₆H₃(C₆H₅)₂‐2,6‐O}{C₆H₃(Me₃C)₂‐2,6‐O}(DME)] 4 are reported.